I may soon be rennovating a 3-story 1880 brick row house in Pittsburgh, and want to insulate the walls. One wall has no windows and is in a narrow alley. Is there an inexpensive way to insulate this whole wall on the exterrior side to minimize lost internal space from framing in walls? The wall is 3 stories tall, in an unused 3 foot wide allley/walkway, and is older double brick construction. The wall is not veneer, so it supports internal structures in the building.